Alloy



Patented June 28, 1027.

UNITED STATES PATENT- OFFICE.

OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK. 4

WILLIAM E. RUDER,

ALLOY.

Io Drawing. Application filed June 7,1923, Serial No. 644,057. Renewed April 29, 1927.

My invention relates to alloys and has for its object the provision of an alloy which is heat resisting or capable of withstanding high temperatures without excessive oxida- I tion.

More specifically my invention relates to alloys which may be cast to form various articles required to withstand high temperatures, such as annealing boxes, furnace structures, etc., and also to electric resistance heating alloys.

I have found that an alloy having an iron base and containing from to percent of nickel, 7 to 9 percent of aluminum, and 7 to 15 percent of chromium forms avery satisfactory material for castings required to. withstand high temperatures. About 1 percent each of a suitable purifying and grain refining material, such as titanium, manganese, or both, may and preferably is added for the purpose of improving the and .15 percent of silicon is satisfactory for my purpose.

In making the alloy it is preferable to use an electric furnace since it lends itself more readily to the controlling of the alloy. The furnace should preferably have a basic lin-' ing since if an acid lining were used a certain amount of silicon in the lining would be reduced by the aluminum and enter into the alloy. Even a small percentage of silicon in the alloy would be obiectionable. When the aluminum is not added in the furnace but is added in the ladle the basic lining becomes less important.

The iron and nickel andchromium are melted in the furnace and then tapped on to the aluminum which has been preheated to a molten condition in the ladle. The titanium and manganese are also added in the furnace. Care should be taken to have the iron nickel. chromium mixture thoroughly physical characteristics of the alloy, aldeoxidized before adding it to the aluminum. It 1s preferable to have the carbon as low as though this is not absolutely necessary. The alloy may not and preferably will not conpossible and in case the material used runs tain the percentage of purifying and grain a little higher than approximately .01 perrefining material added to the mixture since cent of carbon. the carbon should be reduced all .ora large portion of it may go ofi with in the furnace before making the alloy. This the slag. Preferably. I use 30 percent of applies also to the elements phosphorus and nickel. 8 percent of 1 1 nd 10 persulphur. None of the furnace slag should so cent of chromium. the remainder consisting be allowed to come into contact with the alsubstantially of iron. loy after the aluminum .has been added. An alloy made up of the various metals The molten aluminum and also the alloy in the percentage ranges given is extremely after the addition of the aluminum should tough and is very readily cast. It may be be kept covered with a special slag of cryolite machined and hence is particularly suitable 01 a cryollte lime mixture to protect it from for castings requiring machining. The alloy Oxidat on. Cryolite is used because of its may also be forged, rolled 0r drawn into SOlUbIlIty for aluminum oxide. Care should wire. Its drawing properties'are impro d be taken to have the metal in the furnace by the addition of the manganese, and prefillst h en ugh o pour cleanly from the erebly a small amount of the manganese ladle. The cooler it is when cast the better should remain in the alloy. It has a resistthe .l ne

ance of approximately 850 ohms per mil. foot and a low temperature coefficient of resistanc e so that it is particularly adapted 45 for use as an electrical resistance heating element. The alloy shows very little oxidation when, run for long periods at temperatures above 1000 degrees C.

The metal forming the base of the alloy 50 may be ordinary low carbon steel or even commercial iron. A steel containing .02 percent or le'ss'of carbon, .04 percent or less of sulphur, .03 percent or less of phosphorus,

When casting the alloy every precaution should be taken to prevent oxidation. This may be done by filling the molds beforehand with a non-oxidizing gas, such as nitrogen or carbon dioxide, or by dusting the molds lightly but thoroughly with cryolite to dissolve the oxide film formed between the ladle and the mold. This prevents the formation of cold shuts and subsequent cracks due to them. The cryolite method is preferred to the gas method.

While I have described a specific embodiment of my invention in accordance with the provisionsgof the patent statutes, it should be understood that I do not limit my invention thereto, since various modifications thereof W111 suggest themselves to those '40 to 60% iron, 25% or more of nickel and smaller amounts but at least 7% each of aluminum and chromium.

251.;A heat resisting alloy havingan iron base and containing from 25 to 40% of nickel, from 7 to 9% of aluminum and from 7 to 15% of chromium.

3. Aheat resisting alloy containing 50% or more of iron, 25% or more of. nickel and 7% or more each of aluminum and chromium. I

4. A heat resisting alloy having an iron base and containing approximately 30% of nickel, 8% of aluminum and 10%of chromium.

5. A heat resisting alloy having aniron base and containing, approximately 30% of nickel, 8% of aluminum, 10% chromium, and 1%of titanium.

6. A heat resisting alloy having an iron base and containing, approximately 30% of nickel, 8% of aluminum, 10% of chromium,

1%;of titanium, and 1% of manganese.

In witness whereof, I have hereunto set my hand this 6th day of June, 1923.

WHJLIAM E. RUDER. 

